(a) Field of the Invention
The present invention relates to a direction control antenna and a method of controlling the same. More particularly, the present invention relates to a small direction control antenna that can be mounted in a small output wireless transmission apparatus and a method of controlling the same.
(b) Description of the Related Art
In general, in a communication system using a small output wireless transmission apparatus, a terminal, a communication node, and a wireless repeater have a single radio frequency (RF) port and operate with low power. Therefore, a direction control antenna that is used for the wireless transmission apparatus has a small size and has low power consumption for direction control.
FIG. 1 is a perspective view illustrating a direction control antenna having a conventional single RF port.
As shown in FIG. 1, the direction control antenna includes a radiator 20 that is mounted at the center of a ground body 10, and a plurality of parasitic elements 30 that are arranged in a circular shape on the ground body 10 at a periphery of the radiator 20. In this case, a gap d1 between the parasitic element 30 and the parasitic element 30 and a gap d2 between the radiator 20 and the parasitic element 30 are designed to be about ¼ of a wavelength of a frequency using in the direction control antenna, and a radius of the ground body 10 is designed to be about ½ of the wavelength. In such a direction control antenna, at a lower end of each parasitic element 30, a predetermined capacity of an impedance element such as a capacitor is connected to the ground body 10 through a switch, on/off of each switch is determined according to the control of a controller, and a direction is determined and radiation is performed according to a combination of the parasitic elements 30 that are connected to the turn-on switch.
In a small output wireless transmission apparatus, for direction control, when forming a direction control antenna having a small single RF port, if the parasitic element 30 is used, in order to minimize interference between the parasitic elements 30 and between the radiator 20 and the parasitic element 30, it is necessary to form a predetermined gap between the parasitic elements 30 and between the radiator 20 and the parasitic element 30. Further, in order to form a radiation direction along a horizontal plane, a separation distance is necessary between the parasitic element and a boundary of the ground surface. Therefore, the size of the direction control antenna increases. In general, the size of the direction control antenna becomes about one wavelength of a frequency in which a diameter of a ground body uses.
Further, in order to perform direction control in all directions, the parasitic element 30 should be disposed in a symmetrical structure about the radiator 20 and is thus appropriate for a configuration of six sectors of a circular disposition structure, and the number of controllable sectors is limited.